As described in U.S. Patent App. Pub. No. 2016/0135372 to CNH America LLC, which is incorporated by reference herein in its entirety, combine harvesters are typically equipped with a preparation section and a cleaning section. The terms combine harvester, combine and harvester may be used interchangeable herein. The preparation section is located underneath the threshing drums of the harvester and receives a mixture of grain and material other than grain (MOG) from which the grain needs to be further separated. The function of the preparation section is to move the mixture progressively towards the cleaning section, the latter comprising a set of sieves, configured to sieve the mixture and to obtain the separated grains that fall through the sieves, while heavier MOG is collected at the rear of the sieves and lighter MOG is blown towards the rear by a blower producing an air stream in between the sieves.
The preparation section that is most widely applied is the reciprocating grain pan, which is arranged to oscillate backwards and forwards in the longitudinal direction of the harvester so as to move the mixture towards the cleaning section. This setup has the advantage that it uses the differing densities of grain vs. MOG in combination with a reciprocating motion to stratify the mixture with denser grain moving to the bottom of the mixture and lighter MOG material moving toward the top, thus partially pre-separating the MOG from the grain before delivering it to the sieves. On the other hand, the reciprocating grain pan is a relatively passive means of transport, and is therefore subject to negative effects on conveyance due to gravity when harvesting on hilly terrain.
Another known separation means comes in the form of an auger bed, which is composed of a plurality of augers oriented generally in the longitudinal direction of the machine. These augers convey the mixture from the threshing chamber to the sieves with relatively little effect from machine inclination. The augers also deliver a nearly constant flow of material to the sieves, unlike the grain pan which demonstrates a more cyclic sloughing of material in time with its reciprocating motion. The disadvantage of an auger bed system is that the rotating augers tend to mix the grain and MOG components as they convey the material creating a mixture that is more difficult to clean.
The use of multiple preparation stages with a separate blower means aiming an air stream at the gaps between subsequent stages is known, for example from WO-A-8100503 or DE8221573U1. Due to the relatively large size of the gaps, a portion of the mixture is in danger of being lost by falling through the gaps. Despite the air stream directed at the gap, part of the mixture may initially move in the backward direction when falling from one stage onto the next, especially when the preparation stages are formed or comprise at least one reciprocating grain pan. This may be the cause of significant losses.
Referring now to the prior art figures, which are reproduced from U.S. Patent App. Pub. No. 2016/0135372 to CNH America LLC, FIG. 1 shows a number of relevant components in a combine harvester including a preparation section that prepares the crop mixture received from the threshing rotors and transports said mixture towards a cleaning section. The threshing rotors 1, which are shown schematically, are shown oriented in the longitudinal direction of the harvester. Detailed views of the threshing rotors are shown, for example, in U.S. Pat. No. 8,282,453 to CNH America LLC, which is incorporated by reference herein in its entirety and for all purposes.
The cleaning section of the harvester comprises a main blower 10 and a set of sieves 20. The main blower 10 is mounted in a manner known as such in the art, for blowing an air stream in between the sieves 20, to thereby blow light MOG material towards the rear of the harvester. Underneath the rotors 1 and upstream of the main blower 10 and the sieves 20, a first preparation pan 2 is mounted, inclined slightly upward with respect to the horizontal direction. The pan 2 has a front edge 3 and a rear (downstream) edge 4 and is connected to a suitable mechanism for actuating a reciprocating movement of the pan, configured to move a mixture of grains and MOG towards the rear edge of the pan, in a manner known as such in the art.
Fixed to the pan 2, and oriented downwards, is a plate 5, provided with upwardly tilted or horizontal fins 6, placed transversally with respect to the harvester's longitudinal direction. Material that advances beyond the rear edge 4 of the first pan 2 falls onto the first fin 6′, thereby crossing a gap 7. As the plate 5 is fixed to the pan 2, it undergoes the same reciprocating movement, so that the grain mixture is progressively transported from the first fin 6′ to the second fin 6″ and so on until the rear edge of the plate 5, each time crossing a gap 7 when moving from one fin to the next. Between each pair of fins, the plate 5 is provided with a slit or a row of holes, or generally any suitable kind of openings 8, allowing the passage of an air stream or air blasts originating from a fan 15 and directed towards the gaps 7. The fan 15 is separate and configured to work independently from the main blower 10. The fan 15 thus represents the independent blower means referred to above. The fan 15 is mounted upstream of the gaps 7 that are present between each pair of consecutive fins 6, and configured to produce an air stream or blasts of air in the direction of the gaps, thereby blowing lighter MOG material from the mixture towards the rear of the harvester, while the heavier grains are maintained on the fins 6.
The fan 15 may, for example, be fixed to the first preparation pan 2, or to the chassis of the harvester. The fan 15 may be mounted in close proximity to the first of the gaps 7, as illustrated in FIG. 1, or it may be placed more upstream, possibly with suitable air guide panels mounted to guide the air from the fan towards the gaps 7. The air stream or blasts produced by the fan 15 are configured to blow lighter MOG towards the rear of the harvester and thereby establish a separation of the mixture prior to the point where the mixture is delivered to the sieves 20. At the rear edge of the plate 5, the mixture is delivered to the sieves 20 of the cleaning section and treated further in the manner known in the art.
The plate 5 makes it possible to provide multiple preparation stages over a short distance, each fin 6 representing a preparation stage, with the grain mixture moving from the front edge of a fin to the rear edge before falling onto the next fin. Every time the mixture falls from one fin onto the next, the air produced by the blower 15 is capable of blowing light MOG material towards the back of the harvester. This facilitates a more thorough pre-cleaning of the mixture. The plate 5 is downwardly oriented as seen in the direction from the front of the harvester to the back, so that the front edge of a fin is located underneath the rear edge of the previous fin. The fins 6 as such are horizontally or slightly upwardly oriented, as shown in the drawings, so as to support the mixture. The fins are preferably overlapping to a degree, i.e. the rear edge of a fin extends beyond the front edge of a subsequent fin.
The size of the openings or slits 8 is configured to allow the passage of air from the fan 15, whilst obstructing the passage of grains and MOG from the mixture that is being carried by the fins 6. In this way, it may not be possible for grain or MOG to ‘fall through’ the gaps 7 in the direction opposite the general direction of movement of the mixture. Even when the holes or slits 8 would allow small particles of the mixture to pass through the holes, any significant flow of material through the gaps 7 is obstructed by the presence of the plate 5. This ensures transport of the mixture with less mixture losses compared to existing systems. Openings 8 are preferably present between each pair of consecutive fins 6.
The plate 5 can be used in combination with other types of grain preparation stages known in the art, such as a conveyor belt 30, as illustrated in FIG. 2.
While the preparation section of the prior art harvester shown in FIGS. 1 and 2 offer advantages over other prior art preparation sections, improvements are continually sought in the separation of grain from material other than grain (MOG) as the grain and MOG mixture is transported from the threshing chamber to the cleaning system.